1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device, and a semiconductor device thus manufactured.
2. Related Art
In the recent field of semiconductor devices, shrinkage in patterning of interconnect trenches, contact holes and so forth has been advancing. Conventionally, the contact holes have been formed into a circular geometry in a plan view, due to resolution power of resist and other problems. Accordingly, also the contacts formed by filling up the contact holes with an electro-conductive material inevitably have a circular geometry in a plan view. However, when the pattern is shrunk, and the contacts having the circular geometry are extremely shrunk in the diameter thereof, the contact resistance between the contacts and interconnects may sometimes exceed a desired value.
Japanese Laid-Open Patent Publication No. 2004-134574 describes a method of manufacturing a semiconductor device, capable of forming a rectangular contact hole without increasing the number of masks nor procedures. An insulating interlayer herein is etched through a resist mask with a specially-selected gas, so as to allow fluorocarbons to deposit more readily on portions of the resist mask having larger inter-pattern distance. On the other hand, the fluorocarbons are less likely to deposit on portions of the resist mask having smaller inter-pattern distance, because only a few flat portions may be available there for the deposition of fluorocarbons.
Accordingly the recession of the pattern edge towards the region having the larger inter-pattern distances may be prevented while etching of the resist mask in the portion having the smaller inter-pattern distances proceeds. Therefore, by etching the insulating interlayer through thus-formed mask, the contact holes formed in the insulating interlayer may be shaped into a rectangular geometry.